It is known to provide enhanced-surface walls for use in heat exchangers and fluid-mixing devices. Such walls typically have a plurality of characters impressed thereon to enhance the surface area, to improve fluid mixing, to promote turbulence, to break up the boundary layer adjacent the surface, to improve heat transfer, etc.
U.S. Pat. No. 5,052,476 A appears to disclose a heat transfer tube having U-shaped primary grooves, V-shaped secondary grooves, and pear-shaped tertiary grooves to increase turbulence and reflux efficiency. The tube is first formed as a plate, and is then rolled into a tube, after which its proximate ends are welded together. The depth of the secondary grooves is said to be 50-100% of the depth of the primary grooves.
U.S. Pat. No. 5,259,448 A appears to disclose a heat transfer tube having rectangularly-shaped main grooves and narrow secondary grooves that intersect the main grooves at an angle. The device appears to be formed flat, rolled or curled, and then welded. The depth of the narrow grooves is said to be 0.02 millimeters (mm). The depth of the main grooves is said to be 0.20-0.30 mm.
U.S. Pat. No. 5,332,034 A appears to disclose a heat exchanger tube having longitudinally-extending circumferentially-spaced ribs with parallel inclined notches to increase turbulence and to increase heat transfer performance.
U.S. Pat. No. 5,458,191 A appears to disclose a heat exchanger tube having circumferentially-spaced helically-wound ribs with parallel inclined notches.
U.S. Pat. No. 6,182,743 B1 appears to disclose a heat transfer tube with polyhedral arrays to enhance heat transfer characteristics. The polyhedral arrays may be applied to internal and external tube surfaces. This reference may teach the use of ribs, fins, coatings and inserts to break up the boundary layer.
U.S. Pat. No. 6,176,301 B1 appears to disclose a heat transfer tube with polyhedral arrays having crack-like cavities on at least two surfaces of the polyhedrons.
US 2005/0067156 A1 appears to disclose a heat transfer tube that is cold- or forge-welded, and that has dimpled patterns thereon of various shapes.
US 2005/0247380 A1 appears to disclose a heat transfer tube of tin-brass alloys to resist formicary (i.e., ant-like) corrosion.
US 2009/0008075 A1 appears to disclose a heat transfer tube having arrays of polyhedrons, with the second array being arranged at an angle with respect to the first.
U.S. Pat. No. 5,351,397 A appears to disclose a roll-formed nucleate boiling pate having a first pattern of grooves separated by ridges, and a second pattern of more-shallow groves machined into the ridges. The second pattern depth is said to be about 10-50% of the depth of the first pattern.
U.S. Pat. No. 7,032,654 B2 appears to disclose a heat exchanger having fins with enhanced-surfaces, and with holes in the fins.
U.S. Pat. No. 4,663,243 A appears to disclose a heat exchanger surface having flame-sprayed ferrous alloy enhanced boiling surfaces.
Finally, U.S. Pat. No. 4,753,849 appears to disclose a heat exchanger tube with a porous coating to enhanced heat transfer.